How does one know if the girl not cumming is due to her, or me? For example I play with this girl for like 10-20 minutes by deep sensual rubbing/fingering and she does get worked up, but still no cum. On the same token I can eat it for the same amount of time with the same result. We have been seeing each other for 3 months casually but she to my knowledge has never came, but she still comes back eagerly.

Some would advocate not caring as I get what I need, but at the same time it would be nice to leave the scene with both parties having experienced the big O.